/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/
/****************************************************************************
 * fs/vfs/fs_read.c
 *
 *   Copyright (C) 2007-2009, 2012-2014 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>
#include <sys/types.h>
#include <sys/socket.h>

#include <unistd.h>
#include <fcntl.h>
#include <sched.h>
#include <errno.h>
#include <tinyara/cancelpt.h>

#include "inode/inode.h"

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: file_read
 *
 * Description:
 *   This is the internal implementation of read().
 *
 * Parameters:
 *   file     File structure instance
 *   buf      User-provided to save the data
 *   nbytes   The maximum size of the user-provided buffer
 *
 * Return:
 *   The positive non-zero number of bytes read on success, 0 on if an
 *   end-of-file condition, or -1 on failure with errno set appropriately.
 *
 ****************************************************************************/

ssize_t file_read(FAR struct file *filep, FAR void *buf, size_t nbytes)
{
	FAR struct inode *inode;
	int ret = -EBADF;

	DEBUGASSERT(filep);
	inode = filep->f_inode;

	/* Was this file opened for read access? */

	if ((filep->f_oflags & O_RDOK) == 0) {
		/* No.. File is not read-able */

		ret = -EACCES;
	}

	/* Is a driver or mountpoint registered? If so, does it support the read
	 * method?
	 */

	else if (inode && inode->u.i_ops && inode->u.i_ops->read) {
		/* Yes.. then let it perform the read.  NOTE that for the case of the
		 * mountpoint, we depend on the read methods being identical in
		 * signature and position in the operations vtable.
		 */

		ret = (int)inode->u.i_ops->read(filep, (char *)buf, (size_t)nbytes);
	}

	/* If an error occurred, set errno and return -1 (ERROR) */

	if (ret < 0) {
		set_errno(-ret);
		return ERROR;
	}

	/* Otherwise, return the number of bytes read */

	return ret;
}

/****************************************************************************
 * Name: read
 *
 * Description:
 *   The standard, POSIX read interface.
 *
 * Parameters:
 *   file     File structure instance
 *   buf      User-provided to save the data
 *   nbytes   The maximum size of the user-provided buffer
 *
 * Return:
 *   The positive non-zero number of bytes read on success, 0 on if an
 *   end-of-file condition, or -1 on failure with errno set appropriately.
 *
 ****************************************************************************/

ssize_t read(int fd, FAR void *buf, size_t nbytes)
{
	ssize_t ret;

	/* read() is a cancellation point */
	(void)enter_cancellation_point();

	/* Did we get a valid file descriptor? */

#if CONFIG_NFILE_DESCRIPTORS > 0
	if ((unsigned int)fd >= CONFIG_NFILE_DESCRIPTORS)
#endif
	{
		/* No.. If networking is enabled, read() is the same as recv() with
		 * the flags parameter set to zero. Note that recv() sets
		 * the errno variables
		 */

#if defined(CONFIG_NET) && CONFIG_NSOCKET_DESCRIPTORS > 0
		ret = recv(fd, buf, nbytes, 0);
#else
		/* No networking... it is a bad descriptor in any event */

		set_errno(EBADF);
		ret = ERROR;
#endif
	}
#if CONFIG_NFILE_DESCRIPTORS > 0
	else {
		FAR struct file *filep;

		/* The descriptor is in a valid range to file descriptor... do the
		 * read.  First, get the file structure. Note that on failure,
		 * fs_getfilep() will set the errno variable.
		 */

		filep = fs_getfilep(fd);
		if (!filep) {
			/* The errno value has already been set */

			ret = ERROR;
		} else {

			/* Then let file_read do all of the work */

			ret = file_read(filep, buf, nbytes);
		}
	}
#endif

	leave_cancellation_point();
	return ret;
}
